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From: Junio C Hamano <gitster@pobox•com>
To: Jim Meyering <jim@meyering•net>
Cc: Marcus Karlsson <mk@acc•umu.se>, git list <git@vger•kernel.org>
Subject: Re: [PATCH] diff: avoid stack-buffer-read-overrun for very long name
Date: Thu, 26 Apr 2012 09:13:03 -0700	[thread overview]
Message-ID: <xmqq62cma2uo.fsf@junio.mtv.corp.google.com> (raw)
In-Reply-To: <87d36uxzfw.fsf@rho.meyering.net> (Jim Meyering's message of "Thu, 26 Apr 2012 17:52:51 +0200")

Jim Meyering <jim@meyering•net> writes:

> What do you think about replacing those two append-if-needed two-liners:
>
>     if (buffer2.len && buffer2.buf[buffer2.len - 1] != '/')
>             strbuf_addch(&buffer2, '/');
>
> by something that readably encapsulates the idiom:
>
>     strbuf_append_if_absent (&buffer2, '/');
>
> (though the name isn't particularly apt, because you might
> take "absent" to mean "not anywhere in the string," so maybe
>   strbuf_append_if_not_already_at_end (ugly) or
>   strbuf_append_uniq
> )

I am not good at names, but strbuf_terminate_with(&buffer2, '/')
perhaps?

> There are several other uses that would benefit from such a transformation:
> To find the easy ones, I ran this:
>
>   git grep -B1 "strbuf_addch.*'"|grep -A1 '!='
>
> I've manually marked/separated the ones that don't apply.
>
> Note how only 2 of the 6 candidates ensure that length is positive
> before using ".len - 1":

Yikes, that is embarrasing ;-)

>
> ------------------------------------
> builtin/branch.c-	if (!buf.len || buf.buf[buf.len-1] != '\n')
> builtin/branch.c:		strbuf_addch(&buf, '\n');
> --
> builtin/fmt-merge-msg.c-		if (out->buf[out->len - 1] != '\n')
> builtin/fmt-merge-msg.c:			strbuf_addch(out, '\n');
> --
> builtin/log.c-		if (filename.buf[filename.len - 1] != '/')
> builtin/log.c:			strbuf_addch(&filename, '/');
> --
> builtin/notes.c-	if (buf.buf[buf.len - 1] != '\n')
> builtin/notes.c:		strbuf_addch(&buf, '\n'); /* Make sure msg ends with newline */
> --
> refs.c-		if (real_pattern.buf[real_pattern.len - 1] != '/')
> refs.c:			strbuf_addch(&real_pattern, '/');
> --
> strbuf.h-	if (sb->len && sb->buf[sb->len - 1] != '\n')
> strbuf.h:		strbuf_addch(sb, '\n');

next prev parent reply	other threads:[~2012-04-26 16:14 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-04-16 15:20 [PATCH] diff: avoid stack-buffer-read-overrun for very long name Jim Meyering
2012-04-16 22:27 ` Marcus Karlsson
2012-04-24 16:09   ` Jim Meyering
2012-04-25 19:37     ` Junio C Hamano
2012-04-26 15:52       ` Jim Meyering
2012-04-26 16:13         ` Junio C Hamano [this message]
2012-04-26 16:21           ` Bert Wesarg
2012-04-26 16:26             ` Jim Meyering
2012-04-26 16:53               ` Bert Wesarg
2012-04-26 17:26                 ` Jim Meyering
2012-04-26 16:22           ` Jim Meyering
2012-04-27 12:55           ` Andreas Ericsson
2012-04-27 15:07             ` Junio C Hamano

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